@Stax: I crashed this thing, no warranty claims here, please no OT banter.

No OT banter from me, just trying to be helpful. I think calfee are the only people that can work on cervelo and leave the warranty intact. So although you are not claiming for this, if your bike developed bb cracks then i think it could be knocked back if worked on by an unauthorised company,but you'd hope not. Worth checking was my point.

Perhaps a frame repair specialist such as the fibre lyte chap will confirm this but this is my two pence:

I believe that when there is any crack like this, the paint in the cracked area is scraped off using a very sharp knife or scalpel. This ensures that you don't go any further through layers than necessary, ie no carbon is removed. This is as opposed to sanding like you have done. You cannot tell how far through the layers you have sanded and therefore can easily sand through the carbon by accident.

You claim to have continued sanding once the paint was gone to see how far down the crack goes. You say you took off a couple of layers of carbon and the crack disappeared. So perhaps the structural integrity of the frame has now been affected now you have sanded through a couple of layers.

Like i say though, perhaps someone here with more knowledge will be able to confirm or dismiss this.

In any case, now you have done the above, i would not go for a simple respray which may be tempting. I would definitely go for a repair/inspection and then get it resprayed.

It's me again, have been busy with other things and had no time to progress the repair. I bought another frame meanwhile and 'parked' the broken frame in the cellar.I now decided to fix it and use it as my commuter/winter bike.

I emailed Fiber Lyte the other day but no reply. They must be fairly busy. Btw I'm based in London.Are Fibre Lyte and HQ Fibre Products still the best in this area? If so, I'll call HQ Fibre Products.

Call me crazy;..but after reading through this whole thread I think the crack is minimal to nothing at all and you should just ride the thing... and just keep an ear out for weird noises. I doubt it will fail at all much less catastrophically even if it does, at absolute worst probably a loosening of the parts that you will be able to see and feel obviously, I have seen frames break at the connections between tubes (headtubes, seatstays, etc) and they never explode, they just sort of get loose and creaky and you can feel/see/hear it always.

My advice is it looks fine and even if it isn't your bike wont explode and kill you so go ride it.

I'd be a bit more cautious with cracks and repairs. When frames are manufactured, they (the good ones) go through tough tests that are much harsher than JRA conditions. Suppose you are descending really fast and there is a really big pothole, it can be very demanding on the frame. Carbon gets its strength by being continuous, so it's hard for patched carbon to be continuous with the original fibers.

Even though many have ridden repair bikes and have not been killed, you don't know under what kind of conditions they rode them.

The way I look at it is this: how much is a cracked frame worth? Probably $20-40 if you ebay it. How much is a repaired frame worth? Well suppose a good frame is worth $800-1000 on ebay, then a broken but repaired one is probably $400-500. I know I wouldn't buy a second hand frame if it's broken and then repaired. I don't care even if Steve Jobs repaired it. So why take the risk?Except maybe if there is emotional value of the item.

Besides, always good to have an extra excuse for getting a new bike, right?

I used them a while back for a customer's Six Carbon which came back better finished than Cannondale supplied it. Pretty cheap too.

Hi Ultimobici,

thanks for the kind reply. Are you referring to Fybre Lite or HQ Fibre Products?

UPDATE: just called Fybre Lite and talked to John, very friendly chap. Will pack the bike and post it in next few days. Will post pictures of repaired bike when finished. He said it's definitely repairable, and very minor.

I'd be a bit more cautious with cracks and repairs. When frames are manufactured, they (the good ones) go through tough tests that are much harsher than JRA conditions. Suppose you are descending really fast and there is a really big pothole, it can be very demanding on the frame. Carbon gets its strength by being continuous, so it's hard for patched carbon to be continuous with the original fibers.

The way I look at it is this: how much is a cracked frame worth? Probably $20-40 if you ebay it. How much is a repaired frame worth? Well suppose a good frame is worth $800-1000 on ebay, then a broken but repaired one is probably $400-500. I know I wouldn't buy a second hand frame if it's broken and then repaired. I don't care even if Steve Jobs repaired it. So why take the risk?Except maybe if there is emotional value of the item.

Have you ever flown in a commercial aircraft??

They have repairs all over them. Just saying.

When the frames are manufactured, the design goes through the tough tests, each individual frame doesn't. I wouldn't want to buy one that has.

It's a case by case scenario if a repair can be done to render something safe again, not a blanket generalisation that it can or cannot.

Fibre Lyte repaired a Cervelo fork for me recently. John did a very neat and extremely well finished job, I was very pleased. Great people to do business with too. I would highly recommend them. I paid a very fair price for the work. Also I am certain they would only do a repair if they were 100% sure it was safe.

I had my r5ca top tube repair after I ran up the back of a car and had it crack. Cannot tell at all now good as before (albeit 20g heavier) and the repairer told be it is now stronger too.

I would be concerned about a 20g increase in weight and the statement of it now being stronger than before.

20g is a LOT of carbon, the entire top tube of a R4ca would weigh about 60g, to add another 3rd of that again in material would change the stiffness and thus how the loads flow through the structure. The "repair" may be stronger, however the overall frame is not stronger as the load paths have changed. Put a big link into a small chain and it still is as strong as a small chain. For a top tube I would expect a weight difference of no more than 5g and typically about 1-3g including paint.

Also some things aren't suitable for repair, we see cases where a top tube has a small visible crack where the handlebar has swung around and impacted it. When we do the Ultrasound scan of the area, we find the majority of the top tube has delaminated and the frame is scrapped.

There are lots of people springing up offering carbon repairs, as it is easy to wrap a bit of carbon around something and give it a nice paint job. However a real repair is a bit different to that and takes into account the entire structure not just the cosmetic finish. When descending a mtn at high speed do you think about the paint finish looking nice or the structure being sound?

Stay safe out there people, a cheap and nasty repair is false economy.

Also some things aren't suitable for repair, we see cases where a top tube has a small visible crack where the handlebar has swung around and impacted it. When we do the Ultrasound scan of the area, we find the majority of the top tube has delaminated and the frame is scrapped.

Tbh, I don't get involved too much with the repairs at our place, John (our special projects director) does them all and his workmanship is better than any I have seen. I've never seen him scrap a frame due to a handlebar cracking a top tube. To give you an idea of his talents he's built a time trial frame, a time trial wheel set and two mountain bikes from scratch as well as a hill climb car and a carbon tubbed sprint car that's currently being built.

whodesigns wrote:

a cheap and nasty repair is false economy.

Very true, but there's also the other end of the scale where extortionate prices are unnecessarily charged.

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